The present technology relates to a solid-state image pickup device and to a method of driving the same. In particular, the present technology relates to a solid-state image pickup device and a method of driving a solid-state image pickup device that are capable of improving image quality.
There has been known a solid-state image pickup device that allows capacitance in a floating diffusion (FD) region provided in a pixel to be variable, and thereby adjusting efficiency of conversion, to a voltage, from an electric charge obtained by receiving light from a subject (for example, see Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2007-516654).
In such a solid-state image pickup device, when a signal amount is small, that is, under a low-illuminance condition, sensitivity of the pixel is increased through reducing capacitance of the FD region, and thereby, conversion efficiency is increased. In contrast, when the signal amount is large, that is, under a high-luminance condition, the sensitivity of the pixel is decreased through increasing the capacitance of the FD region, and thereby, the conversion efficiency is decreased. Thus, dynamic range is increased.
In the solid-state image pickup device in which the capacitance of the FD region is variable, a capacitive element is provided between pixels, that is, on the same plane as that of the FD region and a photoelectric conversion element of the pixel, photoelectric conversion element and the like. The capacitive element is connected to the FD region via a switch for allowing the capacitance to be varied. Through turning on or off the switch, switching between a state in which capacitance is added to that of the FD region and a state in which capacitance is not added to that of the FD region is performed. Thus, conversion efficiency is adjusted.